Annealing process and device of semiconductor wafer

ABSTRACT

A device and method for annealing a wafer. The preferred embodiment includes applying a basic thermal budget to a weakened zone of a wafer, substantially evenly over the weakened zone. The basic thermal budget is insufficient to detach a detachment layer from a remainder of the wafer at the weakened zone. An additional thermal budget is applied locally in an initiation region of the weakened zone to initiate the detachment of the detachment layer at the weakened zone.

FIELD OF THE INVENTION

The present invention relates to a process and device for thermallyannealing a wafer of a semiconductor material for detaching a layer fromthe wafer at an weakened zone or zone of weakness.

BACKGROUND OF THE INVENTION

Wafers are known to be made of a semiconductor material, such assilicon. The SMART-CUT® process, for instance, is known for annealingand detaching a layer from such a wafer at a zone of weakness, is anexample of a process implementing such stages. The surface of layersproduced are desired to satisfy very strict specifications. It is commonto find roughness specifications that must not exceed 5 Angstroms interms of rms (root mean square).

Measurements of roughness are generally taken with an AFM (Atomic ForceMicroscope). With this type of device, the roughness is measured onsurfaces scanned by the tip of the AFM, ranging from 1×1 μm² to 10×10μm², and less commonly to 50×50 μm² or even 100×100 μm².

It is also possible to measure the surface roughness by other methods,such as via a “haze”. This method notably has the advantage of quicklycharacterising the harmony of the roughness over a whole surface. Thehaze, which is measured in ppm, comes from a process using the opticalreflective properties of the surface to be characterized, andcorresponds to an optical “background noise” diffused by the surface dueto its micro-roughness.

It is also to be noted that if the layers are to have certain roughnessvalues, they should also have a harmonious roughness over their wholesurface.

The processes known in the art that allow the detachment of a layer froma wafer of semiconductor material following an annealing do not alwaysresult in layer surface roughness that falls within the aforementionedspecifications. There is thus a need to improve the controlling of theroughness of detached layers following an annealing.

SUMMARY OF THE INVENTION

The invention relates to a device and a method for annealing a wafer anddetaching a layer therefrom. In the preferred embodiment of the method,a basic thermal budget is applied to a weakened zone of a wafersubstantially evenly thereover. The basic thermal budget is insufficientto detach a detachment layer from a remainder of the wafer at theweakened zone. An additional thermal budget is applied locally in aninitiation region of the weakened zone in which the basic thermal budgetis applied. Preferably, the basic thermal budget is just slightly belowthe thermal budget needed for effecting the detachment and is sufficienthigh such that the application of the additional thermal budgetinitiates the detachment in the initiation region, and causes thedetachment to propagate throughout the weakened zone from the initiationregion. The preferred weakened zone extends through a crystalline layerof the wafer, which can comprise a semiconductor material.

In the preferred embodiment, a plurality of heating elements cooperateto provide different amounts of heat to substantially evenly apply thebasic thermal budget. Preferably, the thermal budget is applied with thewafer in substantially vertical orientation, although the wafer can bepositioned in other orientations, including horizontally. The operationof the heating elements is preferably selected to counteract effectsthat can cause concentrated heating in certain areas compared to othersin the weakened zone.

The basic thermal budget can be applied before the application of theadditional thermal budget, or it can be applied concurrently therewith.Preferably, a plurality of wafers are annealed in a same batch, and thebasic and thermal budgets can be applied simultaneously.

A heat-conducting gas is preferably caused a flow over the wafer beingannealed. The flow is controlled over a plurality of regions of thewafer in the preferred embodiment for applying the even basic thermalbudget. The flow of heat conducting gas can be controlled, for example,by flowing the gas across a diffusion barrier damper to the wafer or aperforated heating chamber damper in which the wafer is placed.

The preferred annealing device of the present invention includes apositioner that is configured for holding one or more of the wafers thathave weakened zones to facilitate the detachment of the detachment layeradjacent thereto. A heating assembly is configured for applying thebasic and additional thermal budgets. Preferably, heating elements aredisposed adjacent to different portions of the wafer and a controllerassembly is operably associated with the heating elements forcontrolling the heating of different heating elements to producedifferent amounts of heat, preferably to evenly apply the basic thermalbudget.

The controller assembly can be operably associated with the heatingelements for independently controlling the different heating elements.The heating assembly can include a gas feed for feeding a flow ofheat-conducting gas for transferring heat to the wafer, as well as a gascontrol assembly configured for controlling the distribution of the gasflow in association with the wafer. The gas control assembly can includea diffusion damper to cause the gas to flow in a predetermined manner.The diffusion damper can include a perforated heating chamber in whichthe wafer is received for heating, or can include a diffusion barrier,for example.

The heating elements can extend generally horizontally and arepreferably stacked in a generally vertical direction, such as with thepositioner holding the wafer in a substantially vertical position forheating. The preferred heating elements substantially surround the waferor wafers that are held by the positioner. Also, as indicated above, thepositioner can be configured for holding the wafer substantiallyhorizontally or in other orientations for heating in an alternativeembodiment.

The invention thus provides a more effective way of applying thermalbudgets and detaching a thin layer from donor wafer, such as fortransferring a thin layer to a receiving support substrate. Thethickness of these layers transferred is typically on the order of a fewhundreds or tens of nanometers. The detachment can be followed bysurface treatments to further decrease the roughness of the exposedsurfaces of the attached thin layer, and further steps can be carriedout on this layer, such as epitaxially growing additional layers thereonafter the detachment. These processes can be carried out in themanufacture of, for example, electronic or optoelectronic components.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, aims and advantages of the invention will become clearerupon reading the description below of preferable embodiments of theinvention, given in reference to the annexed drawings in which:

FIG. 1 is a diagrammatic view of an embodiment of an annealing deviceconstructed according to the invention;

FIG. 2 is a diagrammatic view of certain elements associated with aheating chamber thereof;

FIG. 3 is a representation of the distribution of haze on the surface ofa layer produced, according to the prior art;

FIG. 4 is a diagrammatic view of another embodiment of an annealingdevice; and

FIGS. 5 a–5 c are diagrammatic views of annealing device embodiments,showing different ways of orienting a flow of heat conducting gas.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention provides improved control of the roughness of a detachedlayer, and provides a thermal annealing process for a wafer of materialchosen from among the semiconductor materials, for detaching a layerfrom the wafer at an weakened or weakened zone. Preferably, duringannealing:

a basic thermal budget is applied to the wafer, the basic thermal budgetbeing slightly inferior to the budget necessary to detach the layer,this budget preferably being distributed in an even or substantiallyeven manner over the weakened zone;

an additional thermal budget is also applied to the wafer locally in apredetermined region of the weakened zone so as to initiate thedetachment of the layer in this region.

Additional preferred and non-restrictive aspects of this process are thefollowing:

during the application of a global thermal budget, different heatingelements that are located facing the wafer are selectively controlled;

the wafer can be placed substantially vertically, horizontally, or inanother suitable orientation;

the application of a basic thermal budget is carried out in a firststage; then an application of an additional localized thermal budget iscarried out in a second stage;

the application of a basic thermal budget is carried out substantiallysimultaneously with the application of an additional localized thermalbudget;

annealing is applied simultaneously to several wafers;

the flow of heat conducting gas is controlled in the different regionsof the surface of the layer;

the control of the heat conducting gas is carried out using a damper,such as with a diffusion barrier geometry or perforated heating chambergeometry.

The invention also provides a device for the implementation of theinventive process. The preferred device includes:

heating elements configured and arranged to face different parts of eachwafer to be annealed;

a heating control selectively control the heating power produced by eachheating element;

a distribution controller controlling the distribution of heatconducting gas in the device;

In the preferred device, several preferred and non-restrictive featuresare the following: the heating elements extend substantiallyhorizontally;

the heating elements extend substantially horizontally;

the heating elements have a general circular, rounded, or other closedshape;

the heating elements are positioned in a substantially vertical series;

the device comprises a wafer reception area into which the wafers areplaced in a substantially vertical orientation for heating;

the heating elements surround the wafer reception area;

the heating elements extend substantially in parallel planes;

the heating elements extend substantially concentrically in relation toeach other;

the device comprises a wafer reception area into which the wafers areplaced in a substantially horizontal orientation for heating;

the distribution control has a diffusion damper enabling the flow of gasto be provoked according to a desired configuration, placed facing anopening enabling heat conducting gas to be introduced;

the damper has a diffusion barrier geometry;

the damper has a perforated heating chamber geometry;

In reference to FIG. 1, a first embodiment of an annealing deviceconstructed according to the invention is shown. It is noted that thewafers used are preferably made of a semiconductor material, such assilicon, and include a weakened zone, produced as known in the art.

The weakened zone, for instance, can be created via implantation ofatomic species at a predetermined depth in the wafer. The weakened zonepreferably extends in the thickness of the wafer at a substantiallyconstant depth, thus preferably along an internal surface parallel tothe faces of the wafer to define a layer to be detached.

In general, the annealing used with the present invention can be part ofa process of the SMART-CUT® type. The purpose of annealing in this typeof process is to aid in the detachment of the layer of material definedin the thickness of the wafer by the weakened zone in each wafer.

The device 10 in FIG. 1 includes a heating chamber 100 configured toreceive one or more wafers T to subject them to annealing according tothe invention. The longitudinal axis of the device 10 is generallyupright and preferably substantially vertical. Device 10 thus resemblesa vertical oven.

Wafers T are placed preferably substantially vertically in chamber 100,instead of horizontally. The wafers are received in a holder, such asboat 110, which in turn is supported by a support 111. The support 111sits on a lid 112 which closes fire hole 120 of the device 10. Handler130 is configured for handling the wafers T and for introducing thewafers T into the device 10 and retracting them after annealing.Additionally, the chamber 100 is provided with an opening 101 locatedopposite the fire hole 120. A heat conducting gas 102 can be introducedinto the chamber 100 via this opening 101.

A plurality of heating elements 140 preferably surround the chamber 100.These heating elements 140 are disposed one after the other in series ina substantially vertical direction.

Heating elements 140 can be electrodes, for example, capable of emittingheat when they are supplied with electricity.

The preferred device 10 also includes a rotating mechanism 150associated with the boat 110 for rotating the boat 110 that issupporting the wafers T around the longitudinal axis of the device 10during annealing. Additionally, a flow controller 160 for controllingand regulating the flow of heat conducting gas 102. The rotatingmechanism 150 and flow controller 160 contribute to providing an evenheating of the wafers, corresponding to the basic thermal budgetexplained below.

FIG. 2 provides an enlarged view of certain aspects of the chamber 100,the wafers T, and the heating elements 140. A smaller number of heatingelements 140 than is preferred is shown in the figures for the purposeof clarity. A heating controller 170 is associated with the heatingelements 140 preferably for selective controlling of the electric supplyof each heating element 140, so as to selectively control the heatprovided by each of these heating elements 140. In this manner, thevertical distribution of the thermal budget applied to the wafers duringheating can be controlled.

A typical vertical oven into which wafers are placed vertically,however, produces vertical temperature gradients. After the detachmentof the layer from each wafer, such gradients result in a verticalgradient of roughness on the surface of the detached portions of thewafer that has a negative effect on the evenness of the surface of thelayer. The roughness is distributed generally in horizontal strata orplies 310 in these typical vertical ovens, the roughness valves are noteven across the surface of the detached layer (on the part of the waferlocated on the opposite side of the weakened zone). Such an effect isshown in FIG. 3.

In a preferred embodiment, it is possible to selectively control groupsof heating elements to have a same set value for the heating temperaturedesired. This is for example the case in an embodiment in which theheating elements are configured as coils disposed adjacent to eachother.

In this configuration, the electric supplies to each coil can beindividually controlled or the respective electric supply of differentgroups of coils can be independently controlled.

If groups of coils are controlled due to the closeness of the coils,there can exist a hotter zone within the group of coils supplied withelectrical power in a same manner or with the same power (this hotterzone being typically in the middle of the group, not taking into accountthe neighbouring groups of coils). According to the invention such hotzones of the device can be exploited, for example to apply an additionaland localized thermal budget, as explained below. By selectivelycontrolling the electric supply of the heating elements 140 the spacedistribution of the thermal budget applied to the wafers can becontrolled.

It is also to be noted in FIG. 3 that the strata or plies 310 are notstraight bands, but have a complex shape.

This shape is due to the effect of a difference of thermal budgetbetween that applied to the central region 320 of the wafer and to itsside edges 330.

It is also possible to selectively control the flow rate distribution ofconducting gas 102 in a horizontal section of the oven, so as to applythis gas flow rate to different areas of the section with the aim ofcancelling out this unevenness observed on a horizontal section of thewafer. This selective controlling of the flow rate distribution ofconducting gas 102 can be carried out as a complement of the selectivecontrolling of the electric supply of the heating elements 140 describedabove. Thus, generally speaking and as detailed below, the spacedistribution of the thermal budget applied to the wafers T is controlledvia the selective controlling of the electric supply of the differentheating elements 140, and/or via the selective controlling of the flowrate distribution of heat conducting gas 102 on the surface of thewafers T.

It is thus possible to apply to the wafers T a thermal budget that issubstantially evenly spaced out over substantially the entire weakenedzone of each wafer. Preferably, the thermal budget is substantiallyevenly spread out over at least ⅔ of the weakened zone, more preferablyat least ¾, and most preferred over at least 90% thereof. This can bevisualised for example via haze measurements taken on the surface of thelayers after their detachment.

To perform an even budget application to wafers T in a type of device 10as shown in FIGS. 1 and 2, the lower heating elements 141 are typicallysupplied with more electricity than the upper elements 142.

This compensates for the natural tendency of heat to rise in the chamber100, which tends to generate higher temperatures in the upper part ofthis chamber. In this way, the thermal budget applied to the wafers Tcan be even over the entire weakened zone of each wafer T.

More generally speaking, the selective controlling of the individualelectric supplies of the different heating elements 140 enables theprecise controlling of the space distribution of the thermal budgetapplied to the wafers T. This controlling of the space distribution ofthe thermal budget applied to the wafers is to:

apply to the wafers T a thermal budget that is very even over the entireweakened zone of each wafer. This thermal budget (known as basic thermalbudget) is controlled so as to be:

from a qualitative point of view, highly evenly spaced out over theweakened surface of each wafer;

from a quantitative point of view, slightly inferior to the budgetnecessary to detach the layer from the wafer.

in addition, to the basic thermal budget, apply an additional thermalbudget controlled so as only to be applied to a localized area of eachwafer to create a controlled “hot point”. This additional thermal budgetcan be applied for example by selectively supplying electricity to oneor more heating elements, and adding to the aforementioned measures soas to obtain a homogeneous heating of the wafers. It is also possible touse a special distribution of temperature in the annealing device 10,for example by controlling the gas flow, so as to apply the additionalthermal budget.

These two applications of controlled thermal budget can be carried outsequentially one after the other, or substantially simultaneously. Theglobal thermal budget thus applied to the wafers (standardbudget+additional budget) is therefore different to that which would beobtained if the wafers were heated in a traditional vertical oven inwhich the wafers are placed vertically. Indeed, in that case the thermalbudget would have a vertical gradient, as described above. The globalthermal budget thus corresponds to a thermal budget can if desired havea localized hot point, such as in an area of the weakened zone, butpreferably is free of variations that are spread over a large part ofthis zone (for example over at least half of a characteristic quantityof this zone—this quantity typically being its diameter in the case of aweakened zone in the shape of a disk).

The device 10 of FIGS. 1 and 2 corresponds to a preferred embodiment ofan annealing device according to the invention. It is, however, alsopossible to carry out such an even application of a global thermalbudget in other embodiments. FIG. 4 shows a device 20 that is capable ofperforming an annealing process according to the invention on a wafer Tor on a plurality of wafers.

The wafer(s) T extends substantially horizontally, in a heating chamber200. The chamber 200 is provided with an opening 201 for theintroduction of heat conducting gas 202.

It is to be noted that the simplified representation in FIG. 4 shows asingle opening 201 for the introduction of heat conducting gas 202,although it is preferred to configure the opening 201 and itsassociation with chamber 200 to ensure that the flow of this gas on thesurface of the wafer(s) T does not generate undesired unevenness in thethermal budgets absorbed by the different zones of the surface of eachwafer (T). In this regard, one embodiment has several openings 201 forthe introduction of heat conducting gas, with these openings regularlyaround the periphery of the device.

It is also possible, as an alternative or in addition, to place on theinside of the device, facing the opening 201 (or each opening 201),diffusion dampers 220 enabling the gas to flow according to a desiredconfiguration. Such dampers 220 thus guarantee that the flow of gas isharmonious and generally evenly distributed over the surface of thewafer T.

Such dampers 220 can have different geometries, for example:

a diffusion barrier 270 geometry interposed between the gas 202 and thewafers T, meaning that the gas 202 must go around the diffusion barrier270 prior to flowing over the wafers (this type of configuration isillustrated in FIGS. 5 a and 5 c).

a perforated chamber 221 geometry surrounding the wafers, the openings222 of which allow the gas 202 to flow towards and over the wafers T(FIG. 5 b).

In the preferred embodiments, including in a horizontal and verticaloven embodiments, and embodiments holding the wafers in otherorientations, it is possible to control the thermal budget applied tothe wafers via two principal means:

the individual controlling of different heating elements; and

the controlling of the flows of heat conducting gas on the differentregions of the surface of the wafer(s) T.

The devices 20-23 comprise heating elements collectively designated inFIG. 4 by the reference 240. These heating elements 240 can be placedexclusively above the wafers, but it is also possible to double them upvia similar heating elements located under the wafers T, for instance.

The heating elements 240 can include a series of individual heatingelements, for example electrodes, that extend along a horizontal plane.Each heating element can be a circular element placed concentrically inrelation to the other elements, with the different elements havingdifferent diameters. These concentric elements are thus also placedconcentrically in relation to the wafers T when the wafers T latter arein the annealing position.

Controllers for selective and individual controlling of each heatingelement can be avoided. This can produce global thermal budget appliedto the wafers as described above.

The heating elements 240 can also include a single electrode of “hotplate” type in which it is possible to control the distribution oftemperature. It is also possible to replace the elements 240 withcontrolled infrared lamps whose respective electric supplies arepreferably individually controlled.

Different types of heating units can be combined. For instance, elements240 of electrode type, such as in the shape of concentric circularelements, can be combined with infrared lamps that provide supplementaryheat capable of:

locally adjusting the thermal budget applied to the weakened zone so asto constitute an even basic thermal budget; and

also selectively creating a hot point or area in this weakened zone bylocally applying an additional thermal budget.

Preferably, the heating device is capable of carrying out a harmoniousand even heating of the wafers so as to apply an even basic thermalbudget to the weakened zone of these wafers, while being able to apply ahigher thermal budget to a particular region of the weakened zone, bycreating a “hot point” or area in the weakened zone. Preferably, only asingle hot point is produced in one weakened area. This can be obtainedpreferably either by:

individually controlling one or more heating elements so as to createthe hot point via the localized increasing of the heating, such as at aspecific time during annealing or throughout annealing.

according to an alternative embodiment, by exploiting the thermalconfiguration of the annealing device of the wafers in question, such asby exploiting a particular flow of heating gas.

In addition, when the heating elements are controlled so as to apply aneven thermal budget to the weakened zones of the wafers, they create ahot point in the weakened zones, it is possible to use this hot pointduring the annealing process so as to apply the desired additionalbudget.

While operating, the annealing device thus preferably applies an evenbasic thermal budget to the weakened zone of the wafers. More precisely,this basic thermal budget corresponds to an energetic budget slightlyinferior to the budget necessary to detach the layer from the wafer.More precisely, this basic thermal budget corresponds to an energeticbudget slightly inferior to the budget necessary to detach the layerfrom the wafer.

The even, basic thermal-budget is applied so as to reach a budgetslightly inferior to that which is necessary to carry out the detachmentof the layer from each wafer.

In this regard, the localized region having received the additionalthermal budget corresponds to a zone in which the detachment of thelayer is initiated. In this initiating zone, the weakened zone of eachwafer has received the basic thermal budget per surface unit as well asthe additional thermal budget. For each wafer, the sum of these twothermal budgets is sufficient to locally initiate the detachment of thelayer from the wafer in the part of the weakened zone that correspondsto the initiating zone.

This detachment thus preferably propagates through the rest of theweakened zone, which has received, per surface unit, a thermal budgetslightly inferior to that needed to carry out the detachment. In theseconditions, the propagation of the initial detachment preferably issufficient to propagate the complete detachment of the layer.

This detachment thus preferably propagates over the entire surface ofthe weakened zone, which leads to the complete detachment of the layer.The applicant has determined that proceeding in this manner leads tomore even, homogeneous, and lower roughness values compared withtraditional methods in which a preferably even thermal budget is appliedto a wafer weakened-zone, and in which the even thermal budget has avalue sufficient to detach of the layer.

The local application of an additional thermal budget to create a hotpoint can be carried out in a constant manner throughout annealing, forinstance. In this case, the standard budget and the additional budgetare applied substantially simultaneously to the wafers. It isalternatively possible to carry out this local application during aspecific stage of the annealing process, for example at the end ofannealing. It is also possible to treat a plurality of waferssimultaneously according to the invention.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, while in thepreferred embodiment a strained silicon film 3 in transferred, othertypes of films of a semiconductor able to be strained and transferredcan be transferred according to a process of the invention.Additionally, in the semiconductor layers, other constituents may beadded thereto, such as carbon with a carbon concentration in the layerin question of less than or equal to about 50% or more preferably with aconcentration of less than or equal to about 5%. Therefore, it will beunderstood that the appended claims are intended to cover all suchmodifications and embodiments that come within the spirit and scope ofthe present invention.

1. A method of annealing a wafer, comprising: substantially evenlyapplying a homogeneous and even basic thermal budget over at least ⅔ ofa weakened zone of the wafer, the basic thermal budget beinginsufficient to detach a detachment layer from a remainder of the waferat the weakened zone; and applying an additional thermal budget locallyin an initiation region of the weakened zone in which the basic thermalbudget is applied for initiating detachment of the detachment layer atthe weakened zone.
 2. The method of claim 1, wherein the weakened zoneextends through a crystalline layer of the wafer.
 3. The method of claim2, wherein the wafer comprises a semiconductor material.
 4. The methodof claim 1, wherein a plurality of heating elements are operated toprovide different amounts of heat to substantially evenly apply thebasic thermal budget.
 5. The method of claim 4, wherein the basicthermal budget is applied to the wafer in a substantially verticalorientation.
 6. The method of claim 4, wherein the basic thermal budgetis applied to the wafer in a substantially horizontal orientation. 7.The method of claim 1, wherein the basic thermal budget is appliedbefore the application of the additional thermal budget.
 8. The methodof claim 1, wherein the basic and additional thermal budgets are appliedin a concurrent application.
 9. The method of claim 8, furthercomprising applying the basic and additional thermal budgets to thewafer and simultaneously to additional wafers.
 10. The method of claim1, further comprising flowing a heat conducting gas over the wafer andcontrolling the flow over a plurality of regions on the wafer for saidsubstantially evenly applying the basic thermal budget.
 11. The methodof claim 10, wherein the flow of heat conducting gas is controlled byflowing the gas across a diffusion barrier damper to the wafer.
 12. Themethod of claim 10, wherein the flow of heat conducting gas iscontrolled by flowing the gas across a perforated heating chamber damperto the wafer.
 13. The method of claim 1, wherein the basic thermalbudget is sufficiently high such that the application of the additionalthermal budget causes the detachment to propagate through the weakenedzone.
 14. The method of claim 1, wherein the basic and additionalthermal budgets are applied while the wafer is present in a waferannealing device comprising a positioner configured for holding thewafer; and a heating assembly configured for applying the basic andadditional thermal budgets.
 15. The method of claim 14, wherein theheating assembly comprises: a plurality of heating elements disposedadjacent different portions of the wafer; and a controller assemblyoperably associated with the heating elements for controlling theheating of different heating elements to produce different amounts ofheat to substantially evenly apply the basic thermal budget.
 16. Themethod of claim 15, wherein the controller assembly is operablyassociated with the heating elements for independently controlling thedifferent heating elements.
 17. The method of claim 15, wherein theheating assembly comprises: a gas feed for flowing a heat conducting gasfor transferring heat to the wafer; and a gas control assemblyconfigured for controlling the distribution of the gas flow inassociation with the wafer.
 18. The method of claim 17, wherein the gascontrol assembly comprises a diffusion damper configured to cause thegas to flow in a predetermined configuration.
 19. The method of claim18, wherein the diffusion damper comprises a diffusion barrier or aperforated heating chamber in which the wafer is received for heating.20. The method of claim 15, wherein the heating elements extendgenerally horizontally and are stacked in a generally verticaldirection.
 21. The method of claim 20, wherein the positioner isconfigured for holding the wafer substantially vertically for heating.22. The method of claim 20, wherein the heating elements substantiallysurround the wafer held by the positioner.
 23. The method of claim 14,wherein the positioner is configured for holding the wafer substantiallyhorizontally for heating.
 24. The method of claim 1, wherein the basicand additional thermal budgets are applied to provide a reducedroughness on the detached detachment layer.
 25. The method of claim 1,wherein the additional thermal budget is applied to provide a hot pointwithin the weakened zone to initiate the detachment through theremainder of the weakened zone that has only the basic thermal budget.26. The method of claim 1, wherein the basic thermal budget issubstantially even over at least ¾ of the weakened zone.
 27. The methodof claim 1, wherein the basic thermal budget is substantially even overat least 90% of the weakened zone.
 28. The method of claim 1, whereinthe basic thermal budget is substantially even over substantially theentire weakened zone.